公共語言運行庫(CLR)開發系列課程(2)：Pinvoke 進階學習筆記

時間 2019-12-04

標籤公共語言運行 clr 開發系列課程 pinvoke 進階學習筆記简体版

原文原文鏈接

上一章地址
API版本
- 具備字符串參數的API一般有兩種版本
  - GetWindowText
    - GetWindowTextA
    - GetWindowTextW
- 缺省狀況下CLR會自動尋找合適的匹配
  - CharSet=Ansi時尋找A版本
  - CharSet=Unicode尋找W版本
  - CharSet=Auto和平臺相關
- DLLImportAttribute（ExactSpelling=true）會關掉這種行爲
Ref/Out參數（C#關鍵字）
- out=[Out]&
  - C#:out int a
  - IL:[Out] int &a
  - C++:int *pa;
- ref=[In,Out]&
  - C#:ref int a
  - IL:[In,Out] int &a
  - C++:int *pa;
- 我的感受使用Ref/Out 參數P/Invoke CRL會對根據對應關鍵字添加對應IL特性 System.Runtime.InteropServices下面的InAttribute、OutAttribute

引用類型和值類型

非託管C/C++　代碼：struct A{int a;}　html
託管代碼:struct A{int a;}　 class A{int a;}

非託管C/C++代碼	A	A*	A**
A爲值類型	A	ref A	IntPtr a
A爲引用類型	N/A	A	ref A

自定義參數轉換
- 託管類型和非託管類型之間是一對多關係
  - String
    - char */wchar_t *　　
    - char[N]/wchar_t[N] 固定長度的字符串
    - BSTR, Ansi BSTR
- MarshalAsAttribute(UnmanagedType)　
- UnmanagedType 枚舉指定對應非託管類型
- [MarshalAsAttribute(UnmanagedType.LPWSTR)] string A
- 非託管函數：void Func(wchar_t *)
- 託管函數：Public static extern void Func([MarshalAs(UnmanagdType.LPWSTR)] string);
內存管理
- 在數據轉換中須要進行內存分配
- 舉例：
  - C#調用Func(string) Marshal.StringToHGlobalAnsi("balabala")
  - C#調用Func(ref string)
  - C#調用string Func()
- CoTaskMemAlloc / CoTaskMemFree　(分配/釋放內存)　內存交換才使用

實例分析CreateProcess

API原型

BOOL WINAPI CreateProcess(
  _In_opt_    LPCTSTR               lpApplicationName,
  _Inout_opt_ LPTSTR                lpCommandLine,
  _In_opt_    LPSECURITY_ATTRIBUTES lpProcessAttributes,
  _In_opt_    LPSECURITY_ATTRIBUTES lpThreadAttributes,
  _In_        BOOL                  bInheritHandles,
  _In_        DWORD                 dwCreationFlags,
  _In_opt_    LPVOID                lpEnvironment,
  _In_opt_    LPCTSTR               lpCurrentDirectory,
  _In_        LPSTARTUPINFO         lpStartupInfo,
  _Out_       LPPROCESS_INFORMATION lpProcessInformation
);

　　（opt 可選的輸入參數）c++

C#　　

Public static extern bool CreateProcess(
     [In] string applicationName,
     [In,Out] StringBuilder commandName,
   [In] ref SECURITY_ATTRIBUTES processAttributes,
   [In] ref SECURITY_ATTRIBUTES threadAttributes,
   [In] bool inheritHandles,
   [In] uint creationFlags,
   [In] IntPtr lpEnvironment,
   [In] string currentDirectory,
   [In] ref STARTUP_INFO startupInfo,
   [Out] out PROCESS_INFORMATION processInformation
);　api

DLL生命週期
- Dll在第一次調用的時候自動加載，不會自動被釋放，加載不到或者找不到函數就會拋出異常app
- Dll不會自動被卸載,建議作法生命一個外部調用類 DLL會伴隨外部調用類一塊兒被清理卸載函數
- 若是須要手段管理DLL生命週期，只能手動調用LoadLibrary/GetProcAddressui
逆向P/Invoke
非託管代碼到託管代碼這種叫逆向P/Invoke
- 部分API接收函數指針做爲參數spa
- EnumWindows(WNDENUMPROC IpEnumFunc,LPARAM lPararm)　指針
- .NET 程序能夠經過P/Invoke調用　EnumWindows API調試
- CLR可以將Delegate 轉換爲函數指針，EnumWindows 來回調這個函數指針code
- ```
[UnmanagedFunctionPointer(CallingConvention.Winapi)]
delegate bool EnumWindowProc(IntPtr hwnd, IntPtr lParam);
EnumWindow(new EnumWindowProc(MyEnumWindow), IntPtr.Zero);
```

DEMO

 class Program
    { 
        /// Return Type: BOOL->int
        ///hwnd: HWND->HWND__*
        ///lParam: LPARAM->LONG_PTR->int
        [UnmanagedFunctionPointerAttribute(CallingConvention.Winapi)]
        public delegate bool WNDENUMPROC(IntPtr hwnd, IntPtr lParam);
         
        class NativeMethods 
        {
            [DllImport("User32.dll",CallingConvention=CallingConvention.Winapi)]
            public static extern int GetWindowText(IntPtr hwnd, StringBuilder text, int count);
             
            /// Return Type: BOOL->int
            ///lpEnumFunc: WNDENUMPROC
            ///lParam: LPARAM->LONG_PTR->int
            [DllImportAttribute("user32.dll", EntryPoint = "EnumWindows")]
            [return: MarshalAsAttribute(UnmanagedType.Bool)]
            public static extern bool EnumWindows(WNDENUMPROC lpEnumFunc, int lParam); 
        }

        private static bool WNDENUMPROC_Callback(IntPtr hwnd, IntPtr lParam) 
        {
            StringBuilder text = new StringBuilder(255);
            NativeMethods.GetWindowText(hwnd, text, 255);
            Console.WriteLine("窗口名：" + text + ",id=" + hwnd.ToInt32() + ",lParam=" + lParam);
            return true;
        }
        static void Main(string[] args)
        {
            WNDENUMPROC myWNDENUMPROC = new WNDENUMPROC(WNDENUMPROC_Callback); 
            NativeMethods.EnumWindows(myWNDENUMPROC,22);
            Console.Read(); 
        }
         
    }

常見問題
- 拋出DllNotFoundException
  
  找不到DLL通常他會到當前目錄去找或者系統目錄去找 DLL若是實在沒法差錯可使用全路徑+dll名不推薦最好是放相對路徑
- 拋出AccessViolationException
  訪問違規，通常是內存不能夠讀不能夠寫或者一塊兒讀一塊兒寫形成的，一般緣由參數轉換錯誤，類型不對應，長度問題。
- 拋出EntryPointNotFoundException
  API方法入口找不到通常都是方法名寫錯或者調用協定不對
- MDA報錯StackImbalanceMDA
  VS提示報錯，參數錯位調用協定不對
- 返回數據錯誤
  參數是否正確，MarshalAs轉換是否成功，開啓非託管調試查看。

進階DEMO

c++

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <Windows.h>
/*自定義*/
typedef struct Mytype
{
    int i;
    char *s;
    double d;
    struct Mytype *p;
}Mytype;

int TestInt(int a,int b)
{
    return a + b;
}
void TestIntPtr(int *i)
{
    *i = *i * -1;
}
char * TestCharPtr(char *a,char *b)
{
    return strcat(a, b);
}
void TestStructPtr(Mytype *p)
{
    p->i++;
    p->d++;
}
void TestPtrPtr(int **a,int length)
{
    *a = (int*)malloc(sizeof(int)*length);
    memset(*a, 0, sizeof(int)* length);
}
void TestArray(int *a, int length)
{
    for (int i = 0; i < length; i++)
    {
        a[i]++;
    }
}

void TestCallback(void(*pf)())
{
    pf();
}
int TestCharWidth(char *s)
{
    return strlen(s);
}

文件名 Source.cpp

LIBRARY "PInvoke"
    EXPORTS
        TestInt
        TestIntPtr
        TestCharPtr
        TestStructPtr
        TestPtrPtr
        TestArray
        TestCallback
        TestCharWidth
文件名 Source.def

 class Program
    {

        [StructLayoutAttribute(LayoutKind.Sequential)]
        public struct Mytype
        {

            /// int
            public int i;

            /// char*
            [MarshalAsAttribute(UnmanagedType.LPStr)]
            public string s;

            /// double
            public double d;

            /// Mytype*
            public System.IntPtr p;
        }

        /// Return Type: void 
        public delegate void Callback();

        static void CallbackFunction()
        {
            Console.WriteLine("callback invoked");
        }
        /// Return Type: int
        ///a: int
        ///b: int
        [DllImportAttribute("Pinvoke.dll", EntryPoint = "TestInt", CallingConvention = CallingConvention.Cdecl)]
        public static extern int TestInt(int a, int b);


        /// Return Type: void
        ///i: int*
        [DllImportAttribute("Pinvoke.dll", EntryPoint = "TestIntPtr", CallingConvention = CallingConvention.Cdecl)]
        public static extern void TestIntPtr(ref int i);


        /// Return Type: char*
        ///a: char*
        ///b: char*
        [DllImportAttribute("Pinvoke.dll", EntryPoint = "TestCharPtr", CallingConvention = CallingConvention.Cdecl)]
        public static extern System.IntPtr TestCharPtr(System.IntPtr a, System.IntPtr b);


        /// Return Type: void
        ///p: Mytype*
        [DllImportAttribute("Pinvoke.dll", EntryPoint = "TestStructPtr", CallingConvention = CallingConvention.Cdecl)]
        public static extern void TestStructPtr(ref Mytype p);


        /// Return Type: void
        ///a: int**
        ///length: int
        [DllImportAttribute("Pinvoke.dll", EntryPoint = "TestPtrPtr", CallingConvention = CallingConvention.Cdecl)]
        public static extern void TestPtrPtr(ref System.IntPtr a, int length);


        /// Return Type: void
        ///a: int*
        ///length: int
        [DllImportAttribute("Pinvoke.dll", EntryPoint = "TestArray", CallingConvention = CallingConvention.Cdecl)]
        public static extern void TestArray(int[] a, int length);


        /// Return Type: void
        ///pf: Anonymous_5afb5371_1680_4be9_99a9_ab5bd7ded029
        [DllImportAttribute("Pinvoke.dll", EntryPoint = "TestCallback", CallingConvention = CallingConvention.Cdecl )]
        public static extern void TestCallback(Callback pf);


        /// Return Type: int
        ///s: char*
        [DllImportAttribute("Pinvoke.dll", EntryPoint = "TestCharWidth", CallingConvention = CallingConvention.Cdecl)]
        public static extern int TestCharWidth( IntPtr s);

         

        static void Main(string[] args)
        {
           

            Console.WriteLine("TestInt:" + TestInt(11, 2));

            // TestIntPtr
            int i = 22;
            TestIntPtr(ref i);
            Console.WriteLine("TestIntPtr:" + i);



            // TestCharPtr
            IntPtr helloPtr = Marshal.StringToHGlobalAnsi("啊阿斯達斯的阿薩德+");
            IntPtr worldPtr = Marshal.StringToHGlobalAnsi("+阿薩德阿薩德");
            IntPtr helloWorldPtr = TestCharPtr(helloPtr, worldPtr);
            string helloWorld = Marshal.PtrToStringAnsi(helloWorldPtr);
            Console.WriteLine("TestCharPtr:" + helloWorld);
 
            //helloPtr = Marshal.StringToHGlobalUni("啊阿斯蒂芬a");
            //worldPtr = Marshal.StringToHGlobalUni("阿薩德阿薩德");
            //helloWorldPtr = TestCharPtr(helloPtr, worldPtr);
            //helloWorld = Marshal.PtrToStringUni(helloWorldPtr);
            //Console.WriteLine("TestCharPtr01:" + helloWorld);
          //  Marshal.FreeCoTaskMem()
            Marshal.FreeHGlobal(helloPtr);
            Marshal.FreeHGlobal(worldPtr);
     
            // Marshal.FreeHGlobal(helloWorldPtr);  // 由於helloWorldPtr和helloPtr指向的是同一地址，因此再次釋放會報錯

            // TestCharWidth
            string a = "a的";
            IntPtr aPtr = Marshal.StringToHGlobalAnsi(a); // Ansi
            int len = TestCharWidth(aPtr);
            Console.WriteLine("TestCharWidth:" + len);
            a = Marshal.PtrToStringAnsi(aPtr);
            Marshal.FreeHGlobal(aPtr);



            aPtr = Marshal.StringToHGlobalUni(a); // Unicode
            len = TestCharWidth(aPtr); // 值是1，strlen沒有正確處理unicode，因此不要使用strlen測量unicode字符串的長度
            Console.WriteLine("TestCharWidth:" + len);
            a = Marshal.PtrToStringUni(aPtr);
            Marshal.FreeHGlobal(aPtr);

            // TestStructPtr
            Mytype myType = new Mytype { i = 0, d = 1.1, s = a, p = IntPtr.Zero };
            TestStructPtr(ref myType);
            Console.WriteLine("Mytype->i:" + myType.i);
            Console.WriteLine("Mytype->d:" + myType.d);



            // TestArray
            int[] array = new int[] { 1, 2, 3 };
            TestArray(array, array.Length);

            for (int z = 0; z < array.Length; z++)
            {
                Console.WriteLine("array[{0}]" + array[z], z);
            }

            // TestCallback
            TestCallback(CallbackFunction);

            Console.Read();
        }


    }